lib/libc/gen/lockf.c

   1 /*      $NetBSD: lockf.c,v 1.4 2012/06/25 22:32:43 abs Exp $    */
   2
   3 /*-
   4  * Copyright (c) 1997 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Klaus Klein.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: lockf.c,v 1.4 2012/06/25 22:32:43 abs Exp $");
  35 #endif
  36
  37 #include "namespace.h"
  38 #include <errno.h>
  39 #include <fcntl.h>
  40 #include <unistd.h>
  41
  42 #ifdef __weak_alias
  43 __weak_alias(lockf,_lockf)
  44 #endif
  45
  46
  47 int
  48 lockf(int filedes, int function, off_t size)
  49 {
  50         struct flock fl;
  51         int cmd;
  52
  53         fl.l_start = 0;
  54         fl.l_len = size;
  55         fl.l_whence = SEEK_CUR;
  56
  57         switch (function) {
  58         case F_ULOCK:
  59                 cmd = F_SETLK;
  60                 fl.l_type = F_UNLCK;
  61                 break;
  62         case F_LOCK:
  63                 cmd = F_SETLKW;
  64                 fl.l_type = F_WRLCK;
  65                 break;
  66         case F_TLOCK:
  67                 cmd = F_SETLK;
  68                 fl.l_type = F_WRLCK;
  69                 break;
  70         case F_TEST:
  71                 fl.l_type = F_WRLCK;
  72                 if (fcntl(filedes, F_GETLK, &fl) == -1)
  73                         return (-1);
  74                 if (fl.l_type == F_UNLCK || fl.l_pid == getpid())
  75                         return (0);
  76                 errno = EAGAIN;
  77                 return (-1);
  78                 /* NOTREACHED */
  79         default:
  80                 errno = EINVAL;
  81                 return (-1);
  82                 /* NOTREACHED */
  83         }
  84
  85         return (fcntl(filedes, cmd, &fl));
  86 }